class Solution {
public:
    int search(vector<int>& nums, int target) { //朴素二分模板
    int left = 0, right = nums.size() - 1;
    while(left <= right) //=,eg:left=mid+1,[left,right]此区间数据是未知的
    {
        int mid = left + (right - left)/2;  //防止数据溢出
        if(nums[mid] < target) 
            left = mid + 1;
        else if(nums[mid] > target) 
            right = mid - 1;
        else 
            return mid;
    }
    return -1;
    }
};